Plug fuse receptacle structure



g- 1943- E. w. LANDMEIER 2,326,370

PLUG FUSE RECEPTACLE STRUCTURE Filed Aug. 4, 1941 INVENTOR.

ATTORNEYS Patented Aug. 10, 1943 PLUG FUSE RECEPTACLE STRUCTURE Edwin -W. Landmeier, Cincinnati, Ohio, assignor to The Wadsworth Electric Manufacturing 00., Inc., Covington, Ky., a corporation of Kentucky Application August 4, 1941, Serial No. 405,329

6 Claims. (01. 200-433) This invention relates to receptacles for plug type fuses and it is directed particularly to an improved structure in which the respective parts remain in rigid assembly throughout prolonged usage of the apparatus.

The conventional plug fuse 'is made up of a body having a peripheral contact band with screw threads on its surface adapting it to be screwed into the shell of a fuse receptacle. A center contact is provided at the bottom of the plug fuse for engagement with a center contact in the fuse receptacle. The center and peripheral contacts of both the plug fuse and the fuse receptacle are insulated from one another by means of an insulating washer disposed intermediate the center contact and the bottom wall of the fuse shell.

The present invention is directed particularly to fuse receptacles in which the center contact is a headed screw or bolt, the head portion serving as the contact button for engagement with the bottom contact of the fuse plug, while the threaded shank serves as a fastener for clamping the receptacle assembly in position to a base block member or the like. This type of structure is desirable in that it may be assembled quickly with a screw driver or wrench, and may be disassembled with equal ease; whereas, riveting or the like requires special equipment and makes replacement of a worn or burned part difficult. Moreover, the use of a headed screw is desirable in that it permits adjustments to be made, as in switch structures where contact members which must reside in predetermined spaced relationship are in direct electrical connection with the shell or center contact members of the fuse assemblies and held so by the screw. a

However, when a plug fuse is screwed into a receptacle of this type, the center contact of the fuse presses upon the center contact of the receptacle and the frictional engagement of these contacts, one with the other, causes an unscrewing action to be exerted upon the center contact screw of the receptacle assembly each time a fuse plug is removed for replacement purposes. It frequently happens that after several replacements, the center contact screw of the assembly becomes appreciably unloosened and the parts, being no longer clamped together by the screw, are'free to move about to such a degree that short circuiting takes place.

The principal object of the present invention has been to provide a structure in which the center contact screw is locked frictionally or held all) against rotation with respect to the shell so as to withstand any loosening action imposed on it when a fuse plug is removed.

These results, briefly, in the preferred struc tures of the present invention, are accomplished by providing in the fuse shell an insulating washer which is arranged so as to be nonrotatable with respect to the fuse shell and by seating the head of the center contact screw upon a friction member or look washer element supported by the insulating member. In this manner the screw is restrained against movement relative to the insulating washer and the latter, in turn, is restrained against movement relative to the fuse shell.

In the preferred embodiment the insulating washer has a tail portion which extends through an opening cut in the fuse shell wall; for instance, the tail portion may extend through the opening provided in a conventional fuse shell for reception of a terminal connector, The frictlon member in the preferred embodiment is in the form of a double lock washer configurated at its one face for frictional engagement with the insulating washer and at its other face for frictional engagement with the underneath surface of the screw head.

The present application is directed both to the improved lockwasher and the improved insulating washer, that is, the lock washer may be used with an insulating washer of the conventional circular type or the improved insulating washer can be used without the lock washer. However, each complements the other and best results are obtained when both are used.

In the drawing, which discloses preferred cinbodiments of the invention,

Figure 1 is a cross-sectional view showing a fuse receptacle constructed in accordance with the present invention.

Figure 2 is a sectional view taken on the line 22 of Figure 1.

Figure 3 is a perspective view of an insulating washer embodying the present invention.

Figure 4 is a perspective view of a lock washer made in accordance with the invention.

Figure 5 is a perspective View showing a modi- 'fied form of the lock washer.

The base to which the fuse receptacle is attached may be of the conventional form, as illustrated for example in Figure 1, of a block of insulating material I configurated so as to provide a cavity 2 within which the fuse shell 3 may be disposed with its bottom wall 4 resting on the bottom wall 5 of the cavity 2.

The fuseshllis of the conventional type, its periphery having threads 6 formed in it for reception of the threads formed on thebody of a plug fuse. An opening 1 is cut through the side wall of the she11'3 just above its bottom wall so that terminal connector 8 may pass through the open ing and rest in electrical contact with the bottom wall of the fuse shell. The terminal extends beyond the cavity 2 and carries a screw terminal 9 to which a conductor may be at tached. The central portion of the terminal 8.

which resides within the fuse shell preferably is 7 of circular contour so that it engages the bottomv of the shell over a substantial area and at its:

receptacle making it of fork formation for ease V of assembly. The portion E2 of the connector Q which extends beyond'the fuse shell to the terminal 9 outside the fuse cavity isrelativelynar row. 7 V

The insulating washer i3, rests over the central portion of the connector iwithin the shell and it, likewise preferaoly is of circular contour, being of suohdiameter that its periphery overhangs the periphery of the central portion of the connectorfi so as to conceal it. However, the insulating Washer in the structure shown is 'pro-. vided with a tail I13 which projects through the clearance opening lof the fuse shell, thereby prevent n t e ulat n a r o being dtated relative to the shell. The insulating washer I3 is preferably made of insulation board or fiber board of suitable thickness and it is pro vided with an opening it at its center. a

Connector screw it has a head ii which forms thecenter contact of the fuse receptacle assembly. VThe shank'of the screw [8 extends through the respective openingsl l and E in the connector and insul'atingwasher, down through the base of the plug i and into threaded engagement witha connector 59. It will be seen that screw ll serves to fasten all of the parts into a, rigid assembly, pulling the bottom wall of the fuse shell and the terminal connector 19 together against the opposite faces of the base plug I.

Connector l9 may extend inte connection with the switch member in composite switch fuse units or may terminate in a screw connector 2%) to receive the other electrical conductor of a pair.

In the preferred embodiment of the present invention lock washer ;ii is disposed interniediate' the underneath surface of the head of the screw it and the insulating washer iii. The lock Washable that they do not bite 'through'it; Oneor a series of tangs 23 extend from the oppo ite face 2,326,370 M a V andthereby prevents the insulating washer from tending to warp. r In the form shown in Figure 4, the tangs 22 are blunt bosses extending in a generally radial direction at the periphery of the lock washer. In cross section these tangs may be of V shape or rectangular in cross section so that when the lock washer is pressed against the insulating Washer there is considerable pressure at the local Y area of the tangs against the lock washer to prevent its rotation. The tangs 23-struck from the washerand extending in a clockwise direction provide edges 2 which bite intov the metal of V washer from being rotated in a counterclockwise direction These tangs instead of being located at the periphery are disposed. in the body of the he pre e e em odiment a disclo ed n. t e

washer and are of a yielclaole nature so that if subjected to extreme pressure they tend to becom ent ack. up. nto he bod f the a Thus, their I orin. is such that they cannot bite through a fiber board or similar substance of h ch the nsulat g Washer ma be com e A sreviously i dicat d, the struc ure of the insulating washer i3 held mamo atable pos tio wi h spect to the fuse shell and; consequently'thefrictional n a ement is ubstantia The lock Washers may be mi ted in tance. Where he l ke ood of fuse replacement is not great and where .it is desired to m nim ze he-co t; Al aiqmitt ne t 9k. W sh r e ement the, unde neath v u fa e o the screw. h ad maybe se ra ed to. n rease it i t onal one? mee with e. n$ sv ah I e t er in Doe, and to h r tes d e 7 dra i al of l pa ts eld against m mentr a i e to one ano her s ha r eated remeval of the plug fuses does not disturb the firmne s w t ch he rts. a e assemb e or n he c n er contac to be ome loosen d T is a plica n is qnii uatio n t of m oend ne a pl ca q 's r al Na $312 1 file July 1, 1 Q 'S tQ r c ure- Having de r bed m in e tiqnl c a m:

' l- A ce ta le for. a us 15 m isin a hell; a h ad c ntact'memb di o d Within the shell, an i sula i g member Positi ned in e med e the ead Q t on a t emb and the h ll to in u at 'the' same rom on a h n I mutually engaging meansfor holding the insul til s member a d sh l in on-ro atabl relanoted thatthey are suff ciently blunt or 'yield- V of the lock washer at a point adjacent its central er to prevent backward rotation of the screw.

In the preferred structure thelock washer is of sufficien ly large diame er t esid over a su stantial portion of the insu a ng W she a a- This arran ment avoids ca zation of re r at thelq n a or i n-o t e insul tin washer ibnship. and f ictio memb d s o ed inte m dia e the i sulatin m mberand th head o the con a t member said fr t on membe ha n means at one ac for m ona en agin t e su f c t r nsu tinememb a d aving means at itspther face for'frictionaliy enfm d' with n heshe l'and a W s er membe n s iqn d int rm diate th icon a t membe an th she1l,'the said "shell having an opening therei the said washe memb 'ha i s amn o B end ngth oush he shell op ning; wh r by t e was er member ishekliinnqn-miat bl r a onis of such a naturethat 'it 7 V ship with respect to the shell, and friction means intermediate the washer and the center contact member for restraining the contact member against rotation relative to the washer.

3. A fuse receptacle assembly comprising a fuse receptacle shell, a headed contact member having a threaded shank extending through the bottom of the shell and the said shank constituting a screw for fastening the assembly in position, an insulating washer disposed intermediate the head of the contact member and the shell, and a lock washer having tang means struck from its one face to bite into the surface of the insulating washer and having tang means extending from its opposite surface for frictional engagement with the screw head.

4. The combination with a receptacle confi urated for reception of a plug-type fuse and constituting a contact for the peripheral contact thereof, and a headed fastener member residing within said receptacle and constituting an electrical contact for engagement with the bottom contact of a plug fuse, of a washer constructed of insulating material interposed between the fuse receptacle and the head of the fastener member to insulate the same from one another, and a lock washer interposed between the insulating washer and the head of said fastening member, said lock washer having tang means extending from its one face adapted to bite into the insulating washer and having other tan means extending from its other face to bite into the headed portion of the fastening member.

5. The combination comprising a receptacle configurated for reception of a plug-type fuse and constituting a contact for the peripheral contact thereof, and a headed fastener member residing within said receptacle and constituting an electrical contact for engagement with the bottom contact of a plug fuse, of a washer constructed of insulating material interposed between the fuse shell and the head of the fastener member to insulate one from the other, and a lock washer interposed between the insulating washer and the head of said fastening member, said washer including means for holding the same in non-rotatable relationship with respect to said shell.

6. The combination comprising a receptacle configurated for reception of a plug-type fuse and constituting a contact for the peripheral contact thereof, and a headed fastener member residing within said receptacle and constituting an electrical contact for engagement with the bottom contact of a plug fuse, of a washer constructed of insulating material interposed between the fuse shell and the head of the fastener member to insulate the same from one another, and a lock washer interposed between the insulating washer and the head of said fastening member, said insulating washer including means for holding it in non-rotatable relationship with respect to said shell, said lock washer having tang means extending from its one face adapted to bite into the insulating washer and having other tang means extending from its other face to bite into the headed portion of the fastening member.

EDWIN W. LANDMEER. 

